Translation of PCT/EP01/01954 as filed on Feb. 21, 2001.
The invention relates to a method for the manufacture of a cleaning or application sponge, as well as to a cleaning or application device, which is equipped with a corresponding sponge or sponge body.
For the manufacture of cleaning and application sponges, such as are now more particularly used in the home, it is known to initially produce a relatively large block from polyurethane foam, which is parallelepipedic or cubic. The sponge is then worked from this foam block by cutting and/or punching. If in addition gripping depressions are to be made in the sponge or if its edges are to be beveled, the sponge must undergo a subsequent cutting process. The known manufacturing method is disadvantageous in a number of respects.
Firstly the method is very complicated and therefore costly as a result of the numerous method steps to be successively performed. In addition, the foam blocks are not normally produced by sponge manufacturers and are instead bought in from third parties, so that they must firstly be transported to the sponge manufacturer. In order to reduce the very large transportation volume, it is known to compress the foam blocks, but there is still a relatively large transportation volume for a small transportation weight, so that the transportation of the foam blocks is not economical. In addition, the sponge manufacturer must have a large storage space for the foam blocks and this leads to complicated storage.
On punching and/or cutting out the sponges and in particular during their finishing, there is a very considerable material loss or waste, which is neither economical nor good for the environment. The cutting, punching and milling processes only allow very limited shape configurations and in particular it is not or only with great difficulty possible to form undercuts or subject designs, e.g. animal or human representations.
A significant disadvantage of a sponge worked from a foam block is that the pores on the sponge edges are cut open, which is linked with a stability loss of the sponge in these areas. However, during practical use of the sponge, its edges and corner areas are more particularly needed for cleaning or application purposes, so that the use characteristics of the known sponge are inadequate in this respect.
For many applications it is appropriate and necessary to bond the sponge on at least one side with a coating. For this purpose a blank of the coating to be bonded is produced and said coating is then applied by a flame bonding process. However, this procedure is very labor intensive and also not completely safe.
On of the important disadvantages of the known sponges is the uniform pore or cell structure over the entire sponge volume. If a sponge is wetted and used for cleaning purposes, then the moisture is not only forced in the direction of the article to be cleaned or otherwise treated, but also flows onto the fingers holding the sponge and the hand surface of the use supporting the sponge. This consequently does not allow a targeted use of the cleaning liquid or the medium to be applied.
The problem of the invention is to provide a method for the manufacture of a cleaning or application sponge with which, even in the case of a complicated design, manufacture can take place in an inexpensive and environmentally compatible manner. In addition, a cleaning or application device with a corresponding sponge body is to be provided.
With regards to the method this problem is solved in that the sponge body is foamed or expanded in a mould essentially to the final shape or form of the sponge and on the outer surface of the sponge body during said foaming or expansion process and at least in partial areas thereof, but in particular on the complete outer surface, a strengthened or hardened outer skin is produced.
Thus, during the foaming process the sponge body acquires the desired shape, so that little or no subsequent finishing is necessary. Compared with known sponge manufacture the total number of method steps is significantly reduced, so that the sponge can also be inexpensively manufactured. The aforementioned problem relating to the transportation and storage of the foam blocks can be completely avoided with the method according to the invention. As, according to the invention, the sponge is shaped by the cavity of the mould and not by finishing involving material removal, the material losses can be kept very small.
The formation of the hardened outer skin on the outer surface of the sponge body can be obtained in that the method parameters, e.g. the mould temperature, cooling, foam density, foaming pressure, etc., which are controlled by the composition of the plastics material, are adjusted in such a way that on the outer surface of the sponge body is formed the closed, hardened plastics material skin. The hardened outer skin increases the stability of the sponge body and in the areas of the latter used for product application the outer skin is subsequently at least zonally opened or removed, which can e.g. take place by milling, cutting, grinding, peeling, sand blasting or partial dissolving.
Preferably the interior of the sponge body has a closed-cell structure, which can be zonally opened in a following method step. In this way it is possible to leave certain areas of the sponge body in closed cell form, so that these areas on the one hand have an increased stability and on the other it is ensured that the liquid present during use in the sponge body does not pass out at these areas. Preferably the closed-cell foam is only opened in these sponge body areas, which are used for product application, which permits a targeted escape of liquid or medium to be applied from the sponge body.
The opening of a closed-cell foam structure is known per se and can e.g. take place by mechanical bursting using pressure, known as crushing.
The areas of the sponge body, which remain unopened and consequently have a higher strength, can serve as gripping portions for the user. In particular, the sponge body areas to be used for the direct or indirect retention of the sponge body on gripping parts, handles, sticks, etc. can remain closed-pored.
During the foaming process in the mould use is generally made of parting agents, which in the case of the method according to the invention can be removed without additional measures by opening the closed-cell structure on the surface or the opening of the outer skin.
Not only raising the density of the foam material, but also by a suitable temperature control in the foaming moulds, can increase the edge strength of the sponge body. If the foaming reaction takes place in a closed mould e.g. thermally maintained at 30 to 60xc2x0 C. and more plastics material than necessary is filled into the mould cavity, accompanied by compression or compacting this material cross links to a harder structure with the denser outer skin, which continuously passes into a cellular core. Through an appropriate choice of the temperature and the material mixture introduction into the mould cavity, in this way it is possible to obtain planned foam structures and surface structures with high edge strengths.
If, in the aforementioned manner, on the sponge body are to be formed more stable holding or gripping portions or sealed areas, in said sponge body portions the outer skin is not opened.
As a suitable sponge body material flexible polyurethane foam has proved highly satisfactory and its foam density can be between 25 and 80 kg/m3. It is in particular possible to use polyester-PUR foam.
According to a further development of the invention the foam body comprises several differently structured foam body portions. The foam body portions can be prefabricated and are then joined together by bonding or welding.
A preferred manufacturing possibility results from the fact that the mould cavity is subdivided by one or more partitions, particularly in the form of slides, into several chambers. A foam material can be filled into and reacted in each chamber. Prior to the end of the foaming reaction the partitions are removed, e.g. by pulling the sliders, so that the material in the individual chambers can be linked. The chambers can be completely separated from one another by the partitions, but it is e.g. also possible for the chambers, in predetermined portions, e.g. in the central area of the mould cavity, to be connected, so that in this area a connection or mixing of the two foam structures takes place in unhindered manner. However, in the outer circumferential area of the sponge body, due to the partitions located there, there is a clear demarcation between the individual structural areas. In the central area of the sponge body, which preferably represents most of the sponge body volume, there is consequently an intense linking of the two structures, whereas in a relatively small marginal or circumferential area there can be a precise demarcation of the two structures over a limited depth. The sponge body can also be formed from several layers with the same or a different extension.
According to a preferred further development of the invention in the sponge body is formed a storage chamber for a cleaning medium or a medium to be applied with at least one filling opening running to the outside of the sponge body. The storage chamber can contain the medium to be applied, which can be a liquid, dust, powder, tablets or capsules and when the sponge body is used the medium is supplied to the working or application surface of the sponge body, which is either brought about through the open-celled structure of the sponge body in said area and/or by additional application channels, which can e.g. be drilled. The inventive method of foaming the sponge body in the mould offers numerous possibilities for the design of the storage chamber in the form of a cavity introduced into the sponge body. If a prefabricated gripping part, more particularly made from plastic, is fitted to the sponge body, it can contain the storage chamber for the medium to be applied or can do so at least together with a surface of the sponge body. For this purpose the gripping part can have a filling opening through which the medium to be applied can be filled or refilled into the storage chamber. The filling opening can also be closed by a closure, which can be in the form of a shaped cover, stopper or similar closing element. In a preferred development the storage chamber for the medium to be applied is formed in the space between the sponge body and the mounted gripping part.
If a portion of the sponge body remains unopened for the formation of a holding portion, it can be externally grooved, profiled or structured, in order to make it easier for the user to grip the sponge body and guide it during use.
If a separate gripping part is fitted to the sponge body, the latter is fixed in the above indicated manner, more particularly to an unopened sponge body portion and for fixing purposes there is preferably a locking or bracing of the sponge body in the gripping part, so that the latter can continue to be used even when the sponge body is worn and can be provided with a new sponge body. The receptacle of the gripping part can either be completely filled by the sponge body, or it is possible within the gripping part above the sponge body to leave a free space, which can e.g. serve as a storage chamber for the medium to be applied in the manner described hereinbefore.
According to a further development of the invention an inner bag is embedded in the sponge body and is accessible from the outside of the latter. Said inner bag is more particularly constructed as a glove, e.g. made from rubber or plastic, so that a user can invert the glove over her hand and consequently carries a sponge body fitted to the hand and during use thereof she does not come into contact with the cleaning liquid or medium to be applied.
The mould foaming process according to the invention allows the formation of further elements on the sponge body. For example it is possible to shape a suspension loop on the sponge body, or it is also possible to integrate a closing plug for the storage chamber filling opening in captive manner in the sponge body. In addition, a gripping part can be joined to the sponge body, e.g. by means of a hinge joint and can be manufactured together therewith, so that after removing the gripping part from the mould it is merely necessary to swivel it into a position fixed on the sponge body.
The working or application surfaces of the sponge body can be structured. The surface structures can have both a cleaning or application function or can carry information or decorations. The structuring can be relatively flat and areal or can also be in pin or bristle-like form. The projecting surface areas can remain closed or can be opened by eliminating the outer skin. Further measures such as polishing, galvanizing or eroding the mould cavity enable the sponge body surface to be influenced.
The sponge body can be given an antimicrobial finish. For this purpose antimicrobial agents are introduced into the starting material to be foamed or into the mould cavity. The antimicrobial substances are in particular water-soluble substances such as xylite, chlorohexidine salts or cetyl pyridinium chloriol. A subsequent foam body finishing is also possible, in that it is impregnated with antimicrobial agents or the latter are added in liquid, pasty, pulverulent or solid form into the voids of the sponge body. These can be separate voids specifically provided for this purpose. However, it is also possible to add the antimicrobial agents to the cleaning agents, particularly in the form of liquid detergents. If the antimicrobial agents are fed into a void or cavity of the foam body with no or only a few opened walls, the agent continues to act over a long time period. This fundamentally also applies to cleaning and application media. The closed outer skin of the handling area helps to avoid the undesired escape and aids the targeted use of said agent.
This sponge body can be provided with several, separated chambers, which receive agents, which can react with one another on contact. As a result of the cellular structure of the sponge body and/or the pressing together or the sponge body during use, said agents are brought together. This permits a continuous dosing through the cell structure or a forced dosing resulting from the pressing effect on the sponge body.
The sponge body areas where the largely closed outer skin remains, can be provided with information and/or decorations by sand blasting, etching, printing, screen-printing, ink jet printing or laser application.
It can in particular be provided that the sponge body is zonally provided with a coating on its outer surface. This can in particular be brought about in that prior to the foaming of the sponge body said coating is placed in the mould. This leads to the important advantage that the bonding material can be inserted in part-surface or multipart manner and can be distributed over the handling, working or application surface of the sponge body. The bonding materials can be almost randomly freely selected as a result of the good adhesion of PU foams to all possible materials. They can in particular be abrasive sheets, cloths, extruded elastomer fabrics, e.g. having studs, pins or bristles or also silicone bristles. Corresponding inserts are particularly advantageous at corners and edges of the foam-molded sponge body. In the inserts or also directly on the sponge body it is also possible to apply abrasive materials. As a result of the foaming of the sponge body it is possible to embed thereon by foaming round articles made from materials without any affinity, and these can e.g. be suspension loops or metal rings.
A cleaning or application device according to the invention comprises a sponge body with the aforementioned structure and it is in particular provided that a gripping part is applied to the holding portion of the sponge body.
Further details and features of the invention can be gathered from the following description of embodiments with reference to the attached drawings, wherein show: